Assessment of IL-38 Levels in Patients with Acquired Immune-Mediated Polyneuropathies

Cytokines and chemokines in patients with chronic inflammatory demyelinating polyradiculoneuropathy and multifocal motor neuropathy: A systematic review

Advances in the understanding of cytokines have revolutionized mechanistic treatments for chronic inflammatory and autoimmune diseases, as exemplified by rheumatoid arthritis. We conducted a systematic literature review on the role of cytokines and chemokines in chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal motor neuropathy (MMN). Ovid Medline, EMBASE and Web of Science were searched until August 31, 2022 for human studies investigating cytokines levels in CIDP or MMN. Fifty-five articles on 1061 CIDP patients and 86 MMN patients were included, with a median of 18 patients per study (range 3-71). Studies differed in the inclusion criteria, type of assay, manufacturer, control subjects, and tested biological material. Only a minority of studies reported data on disease activity. Interleukin (IL)-6, IL-17, CXCL10, and tumor necrosis factor alpha (TNF-α), were elevated in CIDP compared to controls in most of the studies. IL-6 and TNF-α levels are also correlated with disability. In MMN patients, IL-1Ra was elevated in the majority of the reports. While acknowledging the challenges in comparing studies and the various limitations of the studies, including small patient numbers, particularly in MMN, our review suggests that IL-6, IL-17, CXCL10, and TNF-α might play a role in CIDP pathogenesis. Larger studies are needed in MMN.

Circulating interleukin-38 concentrations in healthy adults

Interleukin (IL)-38 is the latest discovered member of the interleukin-1 family, which has anti-inflammatory properties similar to IL-36Ra. Several studies compared circulating IL-38 concentrations in healthy and diseased populations to characterize its role in both auto-immune and inflammatory pathologies, with both higher and lower concentrations being associated with certain diseases. However, in order to use IL-38 as a biomarker, a reference range in healthy adults is needed. To establish a reference IL-38 circulating concentration, accessible data from 25 eligible studies with IL-38 concentrations in healthy adults was collected. To validate the values found in literature, we measured IL-38 concentrations by enzyme-linked immunosorbent assay (ELISA) in several cohorts from our own institute. Additionally, the effect of blood collection techniques, freeze thawing cycles, and hemolysis on IL-38 measurements was assessed. To evaluate the importance of the genetic background of individuals as confounding factor of IL-38 synthesis, we used publicly available eQTL databases with matched data on allele frequencies in individuals of different ethnicities. Mean IL-38 concentrations in the various studies were weighted by their corresponding sample size, resulting in a weighted mean, and weighted upper and lower limits were calculated by mean ± 2 SD. Differences of over 10.000-fold were found in the weighted means between studies, which could not be attributed to the blood collection method or assessment of IL-38 in plasma or serum. Although IL-38 concentrations were markedly higher in Chinese then in European population studies, we could not show an association with the genetic background. From our analysis, a reference range for circulating IL-38 in healthy adults could thus not yet be established.

Immunobiological Properties and Clinical Applications of Interleukin-38 for Immune-Mediated Disorders: A Systematic Review Study

Exponential growth in the usage of "cytokines" (as seroimmunobiomarkers) has facilitated more accurate prognosis, early diagnosis, novel, and efficient immunotherapeutics. Numerous studies have reported immunopathophysiological and immunopathological processes of interleukin-38 (IL-38). Therefore, in this systematic review article, the authors aimed to present an updated comprehensive overview on the immunobiological mechanisms, diagnostic, and immune gene-based therapeutic potentials of IL-38. According to our inclusion and exclusion criteria, a total of 216 articles were collected from several search engines and databases from the January 2012 to July 2021 time interval by using six main keywords. Physiologic or pathologic microenvironments, optimal dosage, and involved receptors affect the functionalities of IL-38. Alterations in serum levels of IL-38 play a major role in the immunopathogenesis of a wide array of immune-mediated disorders. IL-38 shows anti-inflammatory activities by reduction or inhibition of pro-inflammatory cytokines, supporting the therapeutic aspects of IL-38 in inflammatory autoimmune diseases. According to the importance of pre-clinical studies, it seems that manipulation of the immune system by immunomodulatory properties of IL-38 can increase the accuracy of diagnosis, and decipher optimal clinical outcomes. To promote our knowledge, more collaboration is highly recommended among laboratory scientists, internal/infectious diseases specialists, oncologists, immunologists, diseases-specific biomarkers scientists, and basic medical researchers.

Over-Expression of Immune-Related lncRNAs in Inflammatory Demyelinating Polyradiculoneuropathies

Long non-coding RNAs (lncRNAs) have crucial roles in the pathogenesis of immune-related disorders. However, their role in the pathobiology of inflammatory demyelinating polyradiculoneuropathies remains unclear. In the current study, we measured peripheral expression of four lncRNAs, namely TUG1, FAS-AS1, NEAT1, and GAS5, in patients with acute/chronic inflammatory demyelinating polyradiculoneuropathies (AIDP/CIDP) compared with healthy subjects. Notably, all lncRNAs were over-expressed in patients compared with controls (P < 0.0001 for all lncRNAs). When assessing their expressions in AIDP and CIDP groups separately, TUG1 and NEAT1 were up-regulated in both patient groups compared with controls, yet FAS-AS1 and GAS5 were only up-regulated in CIDP cases. There were remarkable pairwise correlations between expression levels of these lncRNAs in all study groups. Based on the above-mentioned data, we suggest participation of these for lncRNAs in the pathogenesis of inflammatory demyelinating polyradiculoneuropathies. Moreover, FAS-AS1 and GAS5 lncRNAs have type-specific roles in this regard. Future functional studies are needed to elaborate the molecular mechanisms of the contribution of these transcripts in AIDP/CIDP.

Increased Levels of IL-34 in Acquired Immune-Mediated Neuropathies

Interleukin (IL)-34 is ligand for the colony-stimulating factor (CSF)-1 receptor. This cytokine has fundamental roles the pathogenesis of a number of autoimmune and neurologic disorders. However, its role in the pathogenesis of acute and chronic inflammatory demyelinating polyneuropathies (AIDP and CIDP) has not been assessed yet. We measured serum levels of IL-34 33 CIDP cases, 16 AIDP cases, and 33 control subjects using commercial ELISA kits. IL-34 levels were significantly higher in both AIDP (44.87 ± 4.38) and CIDP (44.87 ± 4.38) groups compared with healthy subjects (30.10 ± 1.05) (P = 0.046 and P = 0.01, respectively). Differences between female subgroups were insignificant. However, levels of this cytokine were significantly higher in male subjects with CIDP compared with male controls (P = 0.042). Thus, levels of this cytokine might be regarded as biomarkers for these kinds of autoimmune disorders. Future studies are needed to verify these results and find the molecular mechanism of participation of IL-34 in the pathogenesis of AIDP/CIDP.

High Levels of Il-19 in Patients with Chronic Inflammatory Demyelinating Polyneuropathy

Immune-mediated neuropathies include some specific types such as acute and chronic inflammatory demyelinating polyneuropathy (AIDP and CIDP). Previous studies have demonstrated abnormal cellular or humoral immune responses in these conditions. Although aberrant regulation of several cytokines have been reported in AIDP and CIDP, the significance of interleukin 19 (IL-19) in these conditions have not been elucidated yet. In the current study, we assessed serum levels of IL-19 in 12 CIDP patients (female/male ratio, 4/8), 9 AIDP patients (female/male ratio, 3/6), and 27 normal subjects (female/male ratio. 8/19) using commercial ELISA kits. Notably, we detected higher levels of this cytokine in CIDP patients (136.4 ± 8.57 ng/l) compared with both AIDP patients (93.89 ± 2.26 ng/l) and controls (83.78 ± 1.72 ng/l). However, the differences between AIDP patients and controls were not significant. The current study demonstrates the role of IL-19 in the pathogenesis of CIDP and potentiates this cytokine as a biomarker for this condition.